Multiple measurement mode in a physiological sensor

ABSTRACT

In a physiological sensor that estimates a true parameter value by providing a predicted parameter value, multiple measurements are taken to increase the accuracy of the predicted parameter value. The sensor can be reapplied between measurements to decrease the probability of an erroneous prediction caused by sensor misplacement. Some measurements can be discarded before calculating a predicted parameter value. The physiological sensor can have a plurality of modes, with one of the modes corresponding to multiple measurement process.

PRIORITY CLAIM

This application claims priority benefit under 35 U.S.C. § 119 to provisional application Ser. No. 61/507,469 filed Jul. 13, 2011. The disclosure of this prior application is hereby incorporated by reference in its entirety and should be considered a part of this application.

BACKGROUND

Spectroscopy is a common technique for measuring the concentration of organic and some inorganic constituents of a solution. The theoretical basis of this technique is the Beer-Lambert law, which states that the concentration c_(i) of an absorbent in solution can be determined by the intensity of light transmitted through the solution, knowing the pathlength the intensity of the incident light I_(0,λ), and the extinction coefficient ε_(i,λ) at a particular wavelength λ. In generalized form, the Beer-Lambert law is expressed as:

$\begin{matrix} {I_{\lambda} = {I_{0,\lambda}e^{{- d_{\lambda}} \cdot \mu_{a,\lambda}}}} & (1) \\ {\mu_{a,\lambda} = {\sum\limits_{i = 1}^{n}{ɛ_{i,\lambda} \cdot c_{i}}}} & (2) \end{matrix}$ where, μ_(0,λ) is the bulk absorption coefficient and represents the probability of absorption per unit length. The minimum number of discrete wavelengths that are required to solve EQS. 1-2 are the number of significant absorbers that are present in the solution.

A practical application of this technique is pulse oximetry, which utilizes a noninvasive sensor to measure oxygen saturation (SpO₂) and pulse rate. The sensor has light emitting diodes (LEDs) that transmit optical radiation of red and infrared wavelengths into a tissue site and a detector that responds to the intensity of the optical radiation after absorption by pulsatile arterial blood flowing within the tissue site. Based on this response, a processor determines measurements for SpO₂, pulse rate, and can output representative plethysmographic waveforms. Thus, “pulse oximetry” as used herein encompasses its broad ordinary meaning known to one of skill in the art, which includes at least those noninvasive procedures for measuring parameters of circulating blood through spectroscopy. Moreover, “plethysmograph” as used herein (commonly referred to as “photoplethysmograph,”) encompasses its broad ordinary meaning known to one of skill in the art, which includes at least data representative of a change in the absorption of particular wavelengths of light as a function of the changes in body tissue resulting from pulsing blood.

Pulse oximeters capable of reading through motion induced noise are available from Masimo Corporation (“Masimo”) of Irvine, Calif. Moreover, portable and other oximeters capable of reading through motion induced noise are disclosed in at least U.S. Pat. Nos. 6,770,028, 6,658,276, 6,584,336, 6,263,222, 6,157,850, 5,769,785, and 5,632,272, which are owned by Masimo, and are incorporated by reference herein. Such reading through motion oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all type of monitoring scenarios.

SUMMARY OF THE INVENTION

In a physiological sensor that estimates a true parameter value by providing a predicted parameter value, multiple measurements are taken to increase the accuracy of the predicted parameter value. To decrease the probability of an erroneous prediction caused by sensor misplacement, the sensor can be reapplied between measurements. Some measurements can be discarded before calculating a predicted parameter value.

In one embodiment, a physiological sensor makes blood absorption measurements at a plurality of wavelengths. Blood absorption measurements are made multiple times and the sensor is reapplied between measurements. This helps increase the accuracy of the predicted parameter value and decrease the probability of an erroneous prediction caused by sensor misplacement. The results of each measurement are used to calculate a predicted parameter value corresponding to the measurement. Some of the calculated predicted parameter values can be discarded before averaging the remaining values to obtain a final predicted parameter value. The final predicted parameter value is provided to the user.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an example data collection system capable of noninvasively measuring one or more blood analytes in a monitored patient, according to an embodiment of the disclosure;

FIG. 2 illustrates an exemplary handheld monitor and an exemplary noninvasive optical sensor of the patient monitoring system of FIG. 1, according to embodiments of the disclosure;

FIG. 3 illustrates a block diagram of a multiple measurement process;

FIG. 4 illustrates a block diagram of a predicted parameter calculation process; and

FIG. 5 illustrates a block diagram of a dual mode sensor measurement process.

DETAILED DESCRIPTION Single Measurement Example

A multiple wavelength sensor and a noninvasive multi-parameter patient monitor can make blood absorption measurements at a plurality of wavelengths. For example, blood absorption measurements can be made at eight wavelengths. Advantageously, this rich wavelength data, compared with conventional pulse oximetry, allows a determination of a tissue profile or tissue characterization over a wavelength spectrum.

Multiple Measurement Mode

In a physiological sensor, measurements can be affected by wide variety of environmental factors. In pulse oximetry, these factors can include temperature, altitude, blood perfusion, sensor placement, and other substances in the blood. In particular, sensor placement can have a significant effect on the accuracy of predicted parameter values. Fortunately, sensor placement often can be controlled and adjusted. Unfortunately, it is hard to determine whether a sensor is optimally placed or whether the measurement could benefit from adjustment of the sensor position.

To increase the accuracy of a predicted parameter value, multiple measurements can be taken. Each measurement can yield a distinct set of input values, and each set of input values can produce by calculation a corresponding predicted parameter value. In pulse oximetry, the optical sensor can be reapplied between the measurements to decrease the probability of an erroneous measurement due to improper sensor placement. Optionally, some of the measurements and corresponding predicted parameter values can be discarded. Also optionally, some of the measurements or predicted parameter values can be averaged. The resulting predicted parameter value or values can be displayed to the user.

In one embodiment, at least three separate measurements are taken by a physiological sensor. As will be understood from the disclosure herein, addition measurements can also be taken. During each of the three or more measurements, blood absorption measurements are made at a plurality of wavelengths. The rich wavelength data from each measurement provides a set of input values that can be used to calculate a predicted parameter value for that measurement. After each of the first and second measurements, the sensor can be adjusted or removed and replaced. The user can be prompted to remove and replace the sensor using visual, audio, or physical cues, and the measurement process can be suspended until the sensor is replaced. In some embodiments, the user can indicate that the sensor has been replaced by pressing a button or tapping a touch screen.

After all three measurements have been obtained, for each measurement, the measurement's set of input values can be used to calculate for that measurement a predicted parameter value. From these three predicted parameter values (corresponding to the three distinct measurements), the median predicted parameter value can be selected and averaged with the next closest predicted parameter value. For example, if the predicted parameter values are 88, 89, and 96, the median value, 89, can be averaged with the next closest value, 88. The average of these two values, 88.5, can be reported as the predicted parameter value. The result can be displayed to the user.

In some embodiments, more than three measurements can be taken and more than one predicted parameter value can be dropped. In other embodiments, various known statistical techniques, such as outlier detection algorithms, can be used to select from among the predicted parameter values the predicted parameter value that best characterizes the distribution of parameter values. The selected parameter value can be provided as the final predicted parameter value. In still other embodiments, measurements are selected to be discarded based on the measured input values rather than the predicted parameter values. For example, the mean or median measured input value can be determined, and one or more input values furthest from that determined value can be discarded. Predicted parameter values can be determined for the remaining input values, and the predicted parameter values can be averaged to obtain a final predicted parameter value. Additionally, measurements can be dropped based on a confidence determination of the measurements. For example, in a system configured to take three measurements, if one measurement is found to have low confidence, that measurement can be dropped and the device can instruct the user or care giver to take a fourth measurement. Additional measurements can also be taken until all three measurements have an adequate confidence determination.

Example Embodiment of A Physiological Sensor With Two Modes

In one embodiment, a physiological sensor can have two or more operating modes. Two of the operating modes can be normal and multi modes. The operating mode can be selected by the user before the measurement process begins. The user can be prompted with instructions for the selected mode.

In normal mode, a true parameter value is estimated by providing a predicted parameter value based on a measured set of input values. This mode can be useful where a quick estimate of a predicted parameter value is needed. In multi mode, successive measurements can be taken as described above in the Multiple Measurement Mode section. For example, three separate input values can be measured, and the sensor can be reapplied between measurements. A predicted parameter value can be calculated for each of the measured input values. Optionally, one or more of the predicted parameter values can be dropped and the remaining values can be averaged to yield a final prediction. For example, of three predicted parameter values, the median value can be averaged with the next closest value and provided to the user. The multi-mode can provide a more accurate measurement with a higher confidence than the normal mode.

Reference will now be made to the Figures to discuss embodiments of the present disclosure.

FIG. 1 illustrates an example of a data collection system 100. In certain embodiments, the data collection system 100 noninvasively measure a blood analyte, such as oxygen, carbon monoxide, methemoglobin, total hemoglobin, glucose, proteins, glucose, lipids, a percentage thereof (e.g., saturation) or for measuring many other physiologically relevant patient characteristics. The system 100 can also measure additional blood analytes and/or other physiological parameters useful in determining a state or trend of wellness of a patient.

The data collection system 100 can be capable of measuring optical radiation from the measurement site. For example, in some embodiments, the data collection system 100 can employ photodiodes defined in terms of area. In an embodiment, the area is from about 1 mm2-5 mm2 (or higher) that are capable of detecting about 100 nanoamps (nA) or less of current resulting from measured light at full scale. In addition to having its ordinary meaning, the phrase “at full scale” can mean light saturation of a photodiode amplifier (not shown). Of course, as would be understood by a person of skill in the art from the present disclosure, various other sizes and types of photodiodes can be used with the embodiments of the present disclosure.

The data collection system 100 can measure a range of approximately about 2 nA to about 100 nA full scale. The data collection system 100 can also include sensor front-ends that are capable of processing and amplifying current from the detector(s) at signal-to-noise ratios (SNRs) of about 100 decibels (dB) or more, such as about 120 dB in order to measure various desired analytes. The data collection system 100 can operate with a lower SNR if less accuracy is desired for an analyte like glucose.

The data collection system 100 can measure analyte concentrations, including glucose, at least in part by detecting light attenuated by a measurement site 102. The measurement site 102 can be any location on a patient's body, such as a finger, foot, ear lobe, or the like. For convenience, this disclosure is described primarily in the context of a finger measurement site 102. However, the features of the embodiments disclosed herein can be used with other measurement sites 102, or with a plurality of measurement sites for multiple measurements.

In the depicted embodiment, the system 100 includes an optional tissue thickness adjuster or tissue shaper 105, which can include one or more protrusions, bumps, lenses, or other suitable tissue-shaping mechanisms. In certain embodiments, the tissue shaper 105 is a flat or substantially flat surface that can be positioned proximate the measurement site 102 and that can apply sufficient pressure to cause the tissue of the measurement site 102 to be flat or substantially flat. In other embodiments, the tissue shaper 105 is a convex or substantially convex surface with respect to the measurement site 102. Many other configurations of the tissue shaper 105 are possible. Advantageously, in certain embodiments, the tissue shaper 105 reduces thickness of the measurement site 102 while preventing or reducing occlusion at the measurement site 102. Reducing thickness of the site can advantageously reduce the amount of attenuation of the light because the there is less tissue through which the light must travel. Shaping the tissue in to a convex (or alternatively concave) surface can also provide more surface area from which light can be detected.

The embodiment of the data collection system 100 shown also includes an optional noise shield 103. In an embodiment, the noise shield 103 can be advantageously adapted to reduce electromagnetic noise while increasing the transmittance of light from the measurement site 102 to one or more detectors 106 (described below). For example, the noise shield 103 can advantageously include a conductive coated glass or metal grid electrically communicating with one or more other shields of the sensor 101. In an embodiment where the noise shield 103 includes conductive coated glass, the coating can advantageously include indium tin oxide. In an embodiment, the indium tin oxide includes a surface resistivity ranging from approximately from 30 ohms per square inch to 500 ohms per square inch. In an embodiment, the resistivity is approximately 30, 200, or 500 ohms per square inch. As would be understood by a person of skill in the art from the present disclosure, other resistivities can also be used which are less than 30 ohms or more than 500 ohms. Other conductive materials transparent or substantially transparent to light can be used instead.

In some embodiments, the measurement site 102 is somewhere along a non-dominant arm or a non-dominant hand, e.g., a right-handed person's left arm or left hand. In some patients, the non-dominant arm or hand can have less musculature and higher fat content, which can result in less water content in that tissue of the patient. Tissue having less water content can provide less interference with the particular wavelengths that are absorbed in a useful manner by blood analytes like glucose. Accordingly, in some embodiments, the data collection system 100 can be used on a person's non-dominant hand or arm.

In some embodiments, measurements are made multiple times and the sensor is reapplied to between measurements, either to the original measurement site or to an additional measurement site. The results of each measurement may be used to calculate a predicted parameter value corresponding to the measurement. Taking multiple measurements may increase the accuracy of the data collected, and reapplying the sensor to the measurement site or a new measurement site may decrease the probability of an erroneous prediction caused by sensor misplacement.

The data collection system 100 can include a sensor 101 (or multiple sensors) that is coupled to a processing device or physiological monitor 109. In an embodiment, the sensor 101 and the monitor 109 are integrated together into a single unit. In another embodiment, the sensor 101 and the monitor 109 are separate from each other and communicate one with another in any suitable manner, such as via a wired or wireless connection. The sensor 101 and monitor 109 can be attachable and detachable from each other for the convenience of the user or caregiver, for ease of storage, sterility issues, or the like. The sensor 101 and the monitor 109 will now be further described.

In the depicted embodiment shown in FIG. 1, the sensor 101 includes an emitter 104, a tissue shaper 105, a set of detectors 106, and a front-end interface 108. The emitter 104 can serve as the source of optical radiation transmitted towards measurement site 102. As will be described in further detail below, the emitter 104 can include one or more sources of optical radiation, such as LEDs, laser diodes, incandescent bulbs with appropriate frequency-selective filters, combinations of the same, or the like. In an embodiment, the emitter 104 includes sets of optical sources that are capable of emitting visible and near-infrared optical radiation.

In some embodiments, the emitter 104 is used as a point optical source, and thus, the one or more optical sources of the emitter 104 can be located within a close distance to each other, such as within about a 2 mm to about 4 mm. The emitters 104 can be arranged in an array, such as is described in U.S. Publication No. 2006/0211924, filed Sep. 21, 2006, titled “Multiple Wavelength Sensor Emitters,” the disclosure of which is hereby incorporated by reference in its entirety. In particular, the emitters 104 can be arranged at least in part as described in paragraphs [0061] through [0068] of the aforementioned publication, which paragraphs are hereby incorporated specifically by reference. Other relative spatial relationships can be used to arrange the emitters 104.

For analytes like glucose, currently available non-invasive techniques often attempt to employ light near the water absorbance minima at or about 1600 nm. Typically, these devices and methods employ a single wavelength or single band of wavelengths at or about 1600 nm. However, to date, these techniques have been unable to adequately consistently measure analytes like glucose based on spectroscopy.

In contrast, the emitter 104 of the data collection system 100 can emit, in certain embodiments, combinations of optical radiation in various bands of interest. For example, in some embodiments, for analytes like glucose, the emitter 104 can emit optical radiation at three (3) or more wavelengths between about 1600 nm to about 1700 nm. In particular, the emitter 104 can emit optical radiation at or about 1610 nm, about 1640 nm, and about 1665 nm. In some circumstances, the use of three wavelengths within about 1600 nm to about 1700 nm enable sufficient SNRs of about 100 dB, which can result in a measurement accuracy of about 20 mg/DL or better for analytes like glucose.

In other embodiments, the emitter 104 can use two (2) wavelengths within about 1600 nm to about 1700 nm to advantageously enable SNRs of about 85 dB, which can result in a measurement accuracy of about 25-30 mg/DL or better for analytes like glucose. Furthermore, in some embodiments, the emitter 104 can emit light at wavelengths above about 1670 nm. Measurements at these wavelengths can be advantageously used to compensate or confirm the contribution of protein, water, and other non-hemoglobin species exhibited in measurements for analytes like glucose conducted between about 1600 nm and about 1700 nm. Of course, other wavelengths and combinations of wavelengths can be used to measure analytes and/or to distinguish other types of tissue, fluids, tissue properties, fluid properties, combinations of the same or the like.

For example, the emitter 104 can emit optical radiation across other spectra for other analytes. In particular, the emitter 104 can employ light wavelengths to measure various blood analytes or percentages (e.g., saturation) thereof. For example, in one embodiment, the emitter 104 can emit optical radiation in the form of pulses at wavelengths about 905 nm, about 1050 nm, about 1200 nm, about 1300 nm, about 1330 nm, about 1610 nm, about 1640 nm, and about 1665 nm. In another embodiment, the emitter 104 can emit optical radiation ranging from about 860 nm to about 950 nm, about 950 nm to about 1100 nm, about 1100 nm to about 1270 nm, about 1250 nm to about 1350 nm, about 1300 nm to about 1360 nm, and about 1590 nm to about 1700 nm. Of course, the emitter 104 can transmit any of a variety of wavelengths of visible or near-infrared optical radiation.

Due to the different responses of analytes to the different wavelengths, certain embodiments of the data collection system 100 can advantageously use the measurements at these different wavelengths to improve the accuracy of measurements. For example, the measurements of water from visible and infrared light can be used to compensate for water absorbance that is exhibited in the near-infrared wavelengths.

As briefly described above, the emitter 104 can include sets of light-emitting diodes (LEDs) as its optical source. The emitter 104 can use one or more top-emitting LEDs. In particular, in some embodiments, the emitter 104 can include top-emitting LEDs emitting light at about 850 nm to 1350 nm.

The emitter 104 can also use super luminescent LEDs (SLEDs) or side-emitting LEDs. In some embodiments, the emitter 104 can employ SLEDs or side-emitting LEDs to emit optical radiation at about 1600 nm to about 1800 nm. Emitter 104 can use SLEDs or side-emitting LEDs to transmit near infrared optical radiation because these types of sources can transmit at high power or relatively high power, e.g., about 40 mW to about 100 mW. This higher power capability can be useful to compensate or overcome the greater attenuation of these wavelengths of light in tissue and water. For example, the higher power emission can effectively compensate and/or normalize the absorption signal for light in the mentioned wavelengths to be similar in amplitude and/or effect as other wavelengths that can be detected by one or more photodetectors after absorption. Alternatively, the emitter 104 can use other types of sources of optical radiation, such as a laser diode, to emit near-infrared light into the measurement site 102.

In addition, in some embodiments, in order to assist in achieving a comparative balance of desired power output between the LEDs, some of the LEDs in the emitter 104 can have a filter or covering that reduces and/or cleans the optical radiation from particular LEDs or groups of LEDs. For example, since some wavelengths of light can penetrate through tissue relatively well, LEDs, such as some or all of the top-emitting LEDs can use a filter or covering, such as a cap or painted dye. This can be useful in allowing the emitter 104 to use LEDs with a higher output and/or to equalize intensity of LEDs.

The data collection system 100 also includes a driver 111 that drives the emitter 104. The driver 111 can be a circuit or the like that is controlled by the monitor 109. For example, the driver 111 can provide pulses of current to the emitter 104. In an embodiment, the driver 111 drives the emitter 104 in a progressive fashion, such as in an alternating manner. The driver 111 can drive the emitter 104 with a series of pulses of about 1 milliwatt (mW) for some wavelengths that can penetrate tissue relatively well and from about 40 mW to about 100 mW for other wavelengths that tend to be significantly absorbed in tissue. A wide variety of other driving powers and driving methodologies can be used in various embodiments.

The driver 111 can be synchronized with other parts of the sensor 101 and can minimize or reduce jitter in the timing of pulses of optical radiation emitted from the emitter 104. In some embodiments, the driver 111 is capable of driving the emitter 104 to emit optical radiation in a pattern that varies by less than about 10 parts-per-million.

The detectors 106 capture and measure light from the measurement site 102. For example, the detectors 106 can capture and measure light transmitted from the emitter 104 that has been attenuated or reflected from the tissue in the measurement site 102. The detectors 106 can output a detector signal 107 responsive to the light captured or measured. The detectors 106 can be implemented using one or more photodiodes, phototransistors, or the like.

In addition, the detectors 106 can be arranged with a spatial configuration to provide a variation of path lengths among at least some of the detectors 106. That is, some of the detectors 106 can have the substantially, or from the perspective of the processing algorithm, effectively, the same path length from the emitter 104. However, according to an embodiment, at least some of the detectors 106 can have a different path length from the emitter 104 relative to other of the detectors 106. Variations in path lengths can be helpful in allowing the use of a bulk signal stream from the detectors 106.

The front end interface 108 provides an interface that adapts the output of the detectors 106, which is responsive to desired physiological parameters. For example, the front end interface 108 can adapt a signal 107 received from one or more of the detectors 106 into a form that can be processed by the monitor 109, for example, by a signal processor 110 in the monitor 109. The front end interface 108 can have its components assembled in the sensor 101, in the monitor 109, in connecting cabling (if used), combinations of the same, or the like. The location of the front end interface 108 can be chosen based on various factors including space desired for components, desired noise reductions or limits, desired heat reductions or limits, and the like.

Signal processor 110 may comprise an input component, a calculation component, and an output component. The input component may be configured to receive measurement data 107, such as measured input values, from the physiological sensor 101. The calculation component may be configured to calculate a predicted parameter value from the measurement data. The output component may be configured to provide an indication to the user to remove and replace the physiological sensor at least one time, for example by displaying a prompt in the user interface 112.

The front end interface 108 can be coupled to the detectors 106 and to the signal processor 110 using a bus, wire, electrical or optical cable, flex circuit, or some other form of signal connection. The front end interface 108 can also be at least partially integrated with various components, such as the detectors 106. For example, the front end interface 108 can include one or more integrated circuits that are on the same circuit board as the detectors 106. Other configurations can also be used.

The front end interface 108 can be implemented using one or more amplifiers, such as transimpedance amplifiers, that are coupled to one or more analog to digital converters (ADCs) (which can be in the monitor 109), such as a sigma-delta ADC. A transimpedance-based front end interface 108 can employ single-ended circuitry, differential circuitry, and/or a hybrid configuration. A transimpedance-based front end interface 108 can be useful for its sampling rate capability and freedom in modulation/demodulation algorithms. For example, this type of front end interface 108 can advantageously facilitate the sampling of the ADCs being synchronized with the pulses emitted from the emitter 104.

The ADC or ADCs can provide one or more outputs into multiple channels of digital information for processing by the signal processor 110 of the monitor 109. Each channel can correspond to a signal output from a detector 106.

In some embodiments, a programmable gain amplifier (PGA) can be used in combination with a transimpedance-based front end interface 108. For example, the output of a transimpedance-based front end interface 108 can be output to a PGA that is coupled with an ADC in the monitor 109. A PGA can be useful in order to provide another level of amplification and control of the stream of signals from the detectors 106. Alternatively, the PGA and ADC components can be integrated with the transimpedance-based front end interface 108 in the sensor 101.

In another embodiment, the front end interface 108 can be implemented using switched-capacitor circuits. A switched-capacitor-based front end interface 108 can be useful for, in certain embodiments, its resistor-free design and analog averaging properties. In addition, a switched-capacitor-based front end interface 108 can be useful because it can provide a digital signal to the signal processor 110 in the monitor 109.

As shown in FIG. 1, the monitor 109 can include the signal processor 110 and a user interface, such as a display 112. The monitor 109 can also include optional outputs alone or in combination with the display 112, such as a storage device 114 and a network interface 116. In an embodiment, the signal processor 110 includes processing logic that determines measurements for desired analytes, such as glucose, based on the signals received from the detectors 106. The signal processor 110 can be implemented using one or more microprocessors or subprocessors (e.g., cores), digital signal processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), combinations of the same, and the like.

The signal processor 110 can provide various signals that control the operation of the sensor 101. For example, the signal processor 110 can provide an emitter control signal to the driver 111. This control signal can be useful in order to synchronize, minimize, or reduce jitter in the timing of pulses emitted from the emitter 104. Accordingly, this control signal can be useful in order to cause optical radiation pulses emitted from the emitter 104 to follow a precise timing and consistent pattern. For example, when a transimpedance-based front end interface 108 is used, the control signal from the signal processor 110 can provide synchronization with the ADC in order to avoid aliasing, cross-talk, and the like. As also shown, an optional memory 113 can be included in the front-end interface 108 and/or in the signal processor 110. This memory 113 can serve as a buffer or storage location for the front-end interface 108 and/or the signal processor 110, among other uses.

The user interface 112 can provide an output, e.g., on a display, for presentation to a user of the data collection system 100. The user interface 112 can be implemented as a touch-screen display, an LCD display, an organic LED display, or the like. In addition, the user interface 112 can be manipulated to allow for measurement on the non-dominant side of patient. For example, the user interface 112 can include a flip screen, a screen that can be moved from one side to another on the monitor 109, or can include an ability to reorient its display indicia responsive to user input or device orientation. In certain embodiments, the user interface 112 may present the user with the option to take multiple measurements. For example, the user may be prompted to reapply the sensor 101 and perform an additional measurement or multiple additional measurements. The user interface 112 may indicate whether a measurement was likely to be erroneous, and may request that the user take another measurement. In alternative embodiments, the data collection system 100 can be provided without a user interface 112 and can simply provide an output signal to a separate display or system.

A storage device 114 and a network interface 116 represent other optional output connections that can be included in the monitor 109. The storage device 114 can include any computer-readable medium, such as a memory device, hard disk storage, EEPROM, flash drive, or the like. The various software and/or firmware applications can be stored in the storage device 114, which can be executed by the signal processor 110 or another processor of the monitor 109. The network interface 116 can be a serial bus port (RS-232/RS-485), a Universal Serial Bus (USB) port, an Ethernet port, a wireless interface (e.g., WiFi such as any 802.1x interface, including an internal wireless card), or other suitable communication device(s) that allows the monitor 109 to communicate and share data with other devices. The monitor 109 can also include various other components not shown, such as a microprocessor, graphics processor, or controller to output the user interface 112, to control data communications, to compute data trending, or to perform other operations.

Although not shown in the depicted embodiment, the data collection system 100 can include various other components or can be configured in different ways. For example, the sensor 101 can have both the emitter 104 and detectors 106 on the same side of the measurement site 102 and use reflectance to measure analytes. The data collection system 100 can also include a sensor that measures the power of light emitted from the emitter 104. The data collection system 100 may also be configured to support measurements at a plurality of measurement sites.

FIG. 2 illustrates an example of a monitoring device 200. In the depicted embodiment, the monitoring device 200 includes a finger clip sensor 201 connected to a monitor 209 via a cable 212. In the embodiment shown, the monitor 209 b includes a display 210, control buttons 208 and a power button. Moreover, the monitor 209 can advantageously include electronic processing, signal processing, and data storage devices capable of receiving signal data from said sensor 201, processing the signal data to determine one or more output measurement values indicative of one or more physiological parameters of a monitored patient, and displaying the measurement values, trends of the measurement values, combinations of measurement values, and the like.

The cable 212 connecting the sensor 201 and the monitor 209 can be implemented using one or more wires, optical fiber, flex circuits, or the like. In some embodiments, the cable 212 can employ twisted pairs of conductors in order to minimize or reduce cross-talk of data transmitted from the sensor 201 to the monitor 209. Various lengths of the cable 212 can be employed to allow for separation between the sensor 201 and the monitor 209. The cable 212 can be fitted with a connector (male or female) on either end of the cable 212 so that the sensor 201 and the monitor 209 can be connected and disconnected from each other. Alternatively, the sensor 201 and the monitor 209 can be coupled together via a wireless communication link, such as an infrared link, radio frequency channel, or any other wireless communication protocol and channel.

The monitor 209 can be attached to the patient. For example, the monitor 209 can include a belt clip or straps that facilitate attachment to a patient's belt, arm, leg, or the like. The monitor 209 can also include a fitting, slot, magnet, LEMO snap-click connector, or other connecting mechanism to allow the cable 212 and sensor 201 to be attached to the monitor 209.

The monitor 209 can also include other components, such as a speaker, power button, removable storage or memory (e.g., a flash card slot), an AC power port, and one or more network interfaces, such as a universal serial bus interface or an Ethernet port. For example, the monitor 209 can include a display 210 that can indicate a measurement for glucose, for example, in mg/dL. Other analytes and forms of display can also appear on the monitor 209.

In addition, although a single sensor 201 with a single monitor 209 is shown, different combinations of sensors and device pairings can be implemented. For example, multiple sensors can be provided for a plurality of differing patient types or measurement sites or even patient fingers.

FIG. 3 shows a block diagram of a multiple measurement mode having multiple measurement stages in a physiological sensor system. At block 310, the sensor is applied to a measurement site and the user can be prompted with instructions. The instructions can include an overview of the multiple measurement process. At block 320, a measurement is taken. After the measurement is taken, at block 330, it is determined whether an additional measurement should be taken. The user may be provided with instructions for taking an additional measurement. For example, the user may optionally be prompted at block 340 to remove and replace the sensor before continuing. The user can be prompted to remove and replace the sensor using visual, audio, or physical cues, and the measurement process can be suspended until the sensor is replaced. In some embodiments, the user can indicate that the sensor has been replaced by pressing a button or tapping a touch screen. Although optional, in certain embodiments reapplying the sensor before taking an additional measurement may be beneficial for reducing the chance of measurement error due to an incorrectly applied sensor.

The sensor system may then loop back to blocks 320 and 330 to take a measurement and determine whether additional measurements are needed. After a sufficient amount of measurements have been taken, the predicted parameter value can be calculated at block 350. For example, as described above, where three or more measurements have been taken the median result can be averaged with the next closest result to get a final result. At block 360, the final result is displayed.

FIG. 4 illustrates a block diagram of a predicted parameter calculation process. At block 410, a physiological sensor system obtains a plurality of input values from multiple measurements. In some embodiments, this may be accomplished by the multiple measurement process depicted in FIG. 3. The system determines at block 420 whether one or more of the input values should be dropped from the input value data set. For example, the mean or median measured input value can be determined, and one or more input values furthest from that determined value can be discarded. Additionally, measurements can be dropped based on a confidence determination of the measurements. For example, in a sensor system configured to take three measurements, if one measurement is found to have low confidence, that measurement can be dropped and the sensor system can instruct the user or care giver to take a fourth measurement. The remaining input values which are not discarded are selected at block 440 for use in further calculations.

At block 430, the sensor system calculates a predicted parameter value corresponding to each input value. The sensor system may analyze these predicted parameter values at block 450 to determine whether one or more of the predicted parameter values should be discarded. Predicted parameter values not discarded are selected at block 460 for use in further calculations.

The sensor system at block 470 calculates the final predicted parameter value from these multiple selected predicted parameter values (each corresponding to one of the multiple distinct measurements). In certain embodiments the median predicted parameter value may be selected and averaged with the next closest predicted parameter value. In other embodiments, various known statistical techniques, such as outlier detection algorithms, may be used to choose, from among the predicted parameter values, the predicted parameter value that best characterizes the distribution of parameter values. The chosen parameter value can be provided as the final predicted parameter value. At block 480, the system displays the final predicted parameter value to the user and/or caregiver.

FIG. 5 illustrates a block diagram of a dual mode sensor measurement process for a physiological sensor system. At block 510, the sensor is applied to a measurement site and the user may be prompted with instructions. The instructions may include, at block 520, an option to use a normal mode or a the multiple measurement mode. If normal mode is selected, the sensor system takes a single measurement at block 530 and uses the input value from that measurement to calculate a final predicted parameter value at block 540.

If the multiple measurement mode is selected, the sensor system may take a plurality of measurements at block 550. In some embodiments, this may be accomplished by the multiple measurement process depicted in FIG. 3. For each input value corresponding to a measurement taken, the sensor system at block 560 may calculate a predicted parameter value. At block 570, the final predicted parameter value is calculated based on one or both of the input value data and the predicted parameter value data. Certain embodiments may employ the predicted parameter calculation process of FIG. 4 to calculate the final predicted parameter value. At block 580, the final predicted parameter value is displayed to the user.

Although the foregoing invention has been described in terms of certain preferred embodiments, other embodiments will be apparent to those of ordinary skill in the art from the disclosure herein. Additionally, other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Additionally, it is contemplated that various aspects and features of the invention described can be practiced separately, combined together, or substituted for one another, and that a variety of combination and subcombinations of the features and aspects can be made and still fall within the scope of the invention. Furthermore, the systems described above need not include all of the modules and functions described in the preferred embodiments. Accordingly, the present invention is not intended to be limited by the recitation of the preferred embodiments, but is to be defined by reference to the appended claims.

Those of skill in the art would understand that information and signals can be represented using a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that can be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

Those of skill in the art will further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The various illustrative logical blocks, modules, and circuits described in connection with the embodiments disclosed herein can be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or other form of storage medium known in the art. A storage medium is coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The processor and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. The processor and the storage medium can reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided to enable a person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Thus, the invention is limited only by the claims. 

What is claimed is:
 1. A system for decreasing a probability of an erroneous value of a physiological parameter caused by sensor misplacement, the system comprising: a physiological sensor configured to be applied to a measurement site by a user and to provide measurements indicative of the physiological parameter; a user interface; a computer-readable memory storing executable instructions; and a processor in communication with the computer-readable memory, wherein the processor is configured by the executable instructions to at least: receive an indication of a user selection of a multiple measurement operating mode, wherein the user selection is made from among a plurality of operating modes of the system comprising a normal operating mode and the multiple measurement operating mode, wherein during the normal mode, the physiological parameter is estimated based only on a single measurement, and wherein during the multiple measurement operating mode, the physiological parameter is estimated based on a number of distinct measurements with a reapplication of the physiological sensor to a same measurement site between measurements; in response to receiving the indication of the user selection of the multiple measurement operating mode, output, to the user interface, instructions for the user to obtain the number of distinct measurements using the physiological sensor and to reapply the physiological sensor between each of the distinct measurements; obtain at least some of the distinct measurements of the number of distinct measurements, wherein, to obtain the at least some of the distinct measurements, the processor is configured to: output, to the user interface, instructions for the user to remove the physiological sensor from the measurement site and reapply the physiological sensor to the measurement site, receive an indication from the user that the physiological sensor has been removed and reapplied, and receive from the physiological sensor a measurement indicative of the physiological parameter after receiving the indication from the user that the physiological sensor has been removed and reapplied; determine a confidence value from the number of distinct measurements corresponding to the same measurement site; and calculate a final value for the physiological parameter based on the acquired number of distinct measurements.
 2. The system of claim 1, wherein the indication comprises a sound.
 3. The system of claim 1, wherein the indication comprises a light.
 4. The system of claim 1, further comprising a touch screen user interface, wherein the indication comprises a visual prompt in the touch screen user interface.
 5. The system of claim 1, further comprising a button, wherein the processor is configured to receive the indication of the user selection based on a user interaction with the button and wherein a user interaction that comprises pressing the button identifies that the physiological sensor has been reapplied.
 6. The system of claim 1, further comprising a touch screen user interface configured to receive an indication from the user that the physiological sensor has been reapplied via a user interaction with the touch screen user interface.
 7. The system of claim 1, wherein the number of distinct measurements using the sensor is at least three.
 8. The system of claim 1, wherein the processor is configured by the executable instructions to at least, for at least some measurements of the number of distinct measurements, receive the measurement after identifying that the user has removed and reapplied the physiological sensor.
 9. The system of claim 1, wherein the processor is configured by the executable instructions to at least: discard a measurement of the number of distinct measurements; and calculate, from the remaining number of distinct measurements, the final value for the physiological parameter.
 10. The system of claim 9, wherein the processor is configured by the executable instructions to at least identify which measurement to discard based on one of a mean or a median of values associated with at least some of the number of distinct measurements.
 11. The system of claim 1, wherein the processor is configured by the executable instructions to at least calculate the final value for the physiological parameter based at least partly on averaging values associated with at least some of the number of distinct measurements.
 12. The system of claim 1, wherein the processor is configured by the executable instructions to at least determine the final value for the physiological parameter by selecting, from among values associated with the number of distinct measurements, a single value that characterizes a distribution of the values associated with the number of distinct measurements.
 13. The system of claim 12, wherein the processor is configured by the executable instructions to at least select the single value by an outlier detection algorithm.
 14. The system of claim 1, wherein the processor is configured by the executable instructions to at least output, to the user interface, an option for the user to select the multiple measurement mode from among the plurality of operating modes. 